Can I fold a long budget down to just the chapter totals?

A long budget has to be read at chapter level, either to talk a financier through it or to find your place again. Click the chevron at the left of each Section header and that chapter folds to a small card that still shows its name and its total, so the whole budget reads as a list of chapter numbers.

Fold and unfold

Click the chevron at the left of a Section header. The chapter's lines fold away and the chapter renders as a small stack of cards with its heading and total still on screen.
Click the chevron again to unfold it. Unfold a chapter before you drag lines into it, so its drop positions are on screen.
To jump to a chapter in a budget you have already folded, click a Section in the sidebar Sections list. One click scrolls the budget to that Section. A double click starts renaming it.

The sidebar and the budget fold on their own

The chevrons in the sidebar Sections list and the chevrons on the budget keep separate state, so you can keep the sidebar outline open while the budget itself is folded to chapter level. The sidebar chevron appears on a Section that contains other Sections, because that list shows Sections and never cost lines.

When a financier is going to read it

If the reason you want chapter level is that someone else reads it, build the Offer Document and add the Cost Overview block. It renders one row per Section with its total and a Total footer, which is the chapter-level view as a table you can send. It leaves the way you fold the budget untouched.

Good to know

Folding a chapter changes no number. Its total, and the budget Total in the sidebar footer, are the same folded or unfolded.
What you fold is your own view of the budget, and it stays that way when you come back to it. A colleague's screen keeps its own fold state.